1. Field of the Invention
The present invention relates to a touchpad, and in particular, relates to a touchpad with a double-layer printed circuit board structure.
2. Background of the Related Art
The touchpad has been widely used in electronic products, such as portable computers, PDAs, mobile telephones and other electronic systems. A touchpad apparatus comprises a flat screen on which a user moves the cursor using fingers or conductive equipments such as touch pens. The touchpad apparatus can also be used for extended functions, for example, the function of simulating keyboard input.
An existing double-layer printed circuit board is shown in FIG. 1. The printed circuit board comprises: an X-axis touch-sensitive line 101; a Y-axis touch-sensitive line 102, wherein the touch-sensitive lines 101 and 102 are disposed on the upper layer of a printed circuit board 100; a component layer 107 disposed on the bottom layer of the printed circuit board 100; an insulating layer 108 disposed between the upper layer configured with the X-axis touch-sensitive line 101 and the Y-axis touch-sensitive line 102 and the component layer 107; and an insulating cover 109 attached to the top of the printed circuit board 100, wherein the insulating cover is configured to act as an operating area for touch pens or fingers. Because the X-axis touch-sensitive line 101 and the Y-axis touch-sensitive line 102 are disposed on the upper layer of the printed circuit board 100, to connect to the component layer 107 disposed on the bottom layer of the printed circuit board 100, the X-axis touch-sensitive line 101 and the Y-axis touch-sensitive line 102 must go through the through-holes 105 and 106, respectively. Further, the intersection of the X-axis touch-sensitive line 101 and the Y-axis touch-sensitive line 102 may induce a circuit short. Accordingly, the Y-axis touch-sensitive lines 102 are configured not to connect to each other directly. Instead, the Y-axis touch-sensitive lines 102 are configured to be connected by a carbon film wire 104 printed with carbon ink. Further, an insulator component 103 is disposed between the X-axis touch-sensitive line 101 and the carbon film wire 104 to prevent the circuit short.
The procedure of manufacturing the carbon film wire is complicated and the manufacturing cost is high. In addition, the carbon film wire will be gradually worn out during usage, which influences the electric characters of the carbon film, and further influences the stability of the entire touchpad. As a result, the life time of the touchpad is decreased.